Field
The disclosed concept pertains generally to electrical switching apparatus and, more particularly, to relays, such as, for example, aircraft relays.
Background Information
FIG. 1 shows a conventional electrical relay 2 including a movable contact 4, which makes or breaks a conductive path between main terminals A1 and A2. Terminals X1 and X2 electrically connect to solenoid actuator coil windings 6,8. On many relays, the actuator coil has two separate windings or a partitioned winding used to actuate closure of separable main contacts, such as 10, and to hold the separable main contacts 10 together in a relay closed or on state. The need for the two coil windings 6,8 is the result of the desire to minimize the amount of electrical coil power needed to maintain the relay 2 in the closed state.
A typical normally open relay has a spring (not shown) on its armature mechanism (not shown) that holds the separable main contacts 10 open. In order to initiate movement of the armature mechanism for closure, a relatively large magnetic field is generated to provide sufficient force to overcome the inertia of the armature mechanism and, also, to build up enough flux in the open air gap of its solenoid (not shown) to create the desired force. During closure motion of the armature mechanism, both coil windings 6,8 are energized to produce a sufficient magnetic field. After the main contacts 10 close, the reluctance of the magnetic path in the solenoid is relatively small, and a relatively smaller coil current is needed to sustain the force needed to hold the main contacts 10 together. At this point, an “economizer” or “cut-throat” circuit (not shown) can be employed to de-energize one of the two coil windings 6,8 to conserve power and to minimize heating in the solenoid.
The economizer circuit (not shown) is often implemented via an auxiliary relay contact 12 (E1-E2) that is physically driven by the same solenoid mechanism (not shown) as the main contacts 10. The auxiliary relay contact 12 simultaneously opens as the main contacts 10 close, thereby confirming complete motion of the armature mechanism. The added complexity of the auxiliary contact 12 and the calibration needed for the simultaneous operation makes this configuration relatively difficult and costly to manufacture.
Alternatively, the economizer circuit (not shown) can be implemented by a timing circuit (not shown) which pulses a second coil winding, such as 8, only for a predetermined period of time, proportional to the nominal armature mechanism operating duration, in response to a command for relay closure (i.e., a suitable voltage applied between terminals X1-X2). While this eliminates the need for an auxiliary switch, it does not provide confirmation that the armature mechanism has closed fully and is operating properly.
There is room for improvement in relays.